The present invention relates broadly to the non-invasive measurement and monitoring of the absolute value of intracranial pressure.
Intracranial pressure (ICP) is closely related to cerebral blood flow (CBF). To a first approximation, CBF is determined by the cerebral perfusion pressure (CPP), due to their respective proportionality (CBF=CPP/Resistance). CPP is the difference between arterial blood pressure (BP) and intracranial pressure (ICP), that is, CPP=BP−ICP. Increase in ICP results in smaller values of CPP and CBF. Because of the difficulty of measuring CBF directly, BP and ICP are often measured to assess CPP. In a healthy individual, automatic regulation mechanisms in the body keep BP, ICP, and cerebral vascular resistance within a normal range and CBF is closely matched to the brain metabolic needs. These automatic regulation systems are often non-functional in brain trauma, stroke, hydrocephalic patients, and patients with liver or kidney failure, so that monitoring and management of ICP becomes a critical aspect of medical care. ICP>20 mmHg is recommended threshold for treatment in trauma patients (I Neurotrauma 2007; 24 Supp I: S55-8).
Current ICP monitoring techniques are generally grouped as either invasive or non-invasive.